Underwater seismometer can hear how fast a glacier is moving – ScienceDaily

Scientists have shown that an ocean floor seismometer deployed near the calving front of a Greenland glacier can detect persistent seismic radiation from an avalanche, reminiscent of a slow earthquake.

Basement slide of marine glaciers controls how quickly the ice drains into the ocean. However, direct observation of such basal movement and identifying its controls is challenging: the frontal environment is one of the most difficult to access and seismically noisy—particularly at the surface of the glacier—due to severely cracked ice and extreme weather conditions.

A team of scientists from Hokkaido University, led by Associate Professor Evgeny A. Podolskiy from the Arctic Research Center, used ocean floor and surface seismometers to detect a previously unknown continuous coastal shaking caused by a sliding glacier. Their findings were published in the journal Nature Communications.

Sensors to measure glacier motion can be placed above, in, or under the glacier; However, each approach has its drawbacks. For example, the surface of glaciers is “noisy” due to wind and tidal faults, which can overshadow all other signals; While the interior is quieter, it is the most difficult area to reach. However, all of these sites suffer from common issues such as station drift, thawing, loss of level, cold temperatures, and potential hardware damage by iceberg birth.

In the current study, scientists used an ocean floor seismometer (OBS) deployed near the front of the calves from Bowdoin Glacier (Kangerluarsuup Sermia) to listen for glacial earthquakes caused by the basal movement of the ice. By doing so, they isolated the sensor from near-surface seismic noise, and also overcame all the problems that come with deploying sensors on and nearby the glacier itself. The data they collected from OBS were related to data from seismographs and ice velocity measurements at the ice surface.

Analysis of the data revealed a continuous seismic tremor caused by the glacier. In particular, the large-scale seismic signal (3.5 Hz to 14.0 Hz) detected by OBS correlates well with the movement of the glacier. The scientists were able to identify signals that were not related to glacial basal dynamics. Data from OBS was necessary to establish a relationship between the tremors detected by surface stations and the GPS-recorded displacement of the glacier. In the process, they show that persistent seismic data that has historically been considered “noise” contains signals that can be used to study glacier dynamics.

Scientists have also suggested that the avalanche is similar to slow earthquakes. The characteristics of the Bowdoin-Glacier earthquake remind those of tectonic tremors in Japan and Canada. Moreover, the presence of tremor is consistent with recent theoretical models and cold laboratory experiments.

Using ocean floor seismology, scientists have presented a new way to gather continuous information about glacier earthquakes about the movement of glaciers in an extremely noisy and harsh polar environment. “Future research in this area could focus on replicating and extending the results of this study in other glaciers,” says Evgeny A. Podolskiy. “Experimental support for the relationship between glacier tremors and tectonic tremors suggests that a long-term, multidisciplinary approach would be useful in fully understanding this phenomenon.”

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Materials provided by Hokkaido University. Note: Content can be modified according to style and length.

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